In the past, various techniques have been developed for the purpose of sterilizing or decontaminating biological sludges and wastes. The most common process is the process of mixing lime with the sludge. The reaction of lime with the water in the sludge serves to elevate the temperature of the sludge for a maximum of 100.degree. C.
U.S. Pat. Nos. 4,781,842 and 4,902,431, issued to Nicholson, teach a process to decontaminate wastewater sludge to a level that meets or exceeds U.S. EPA process standards. The process mixes sludge with an alkaline material sufficient to raise the pH of the end product to 12 or higher for at least one day. This process will raise the temperature to 50.degree. C., but will not sterilize the sludge, nor does it eliminate the pathogenic microorganisms.
U.S. Pat. No. 4,306,978, issued to Wurtz, relates to a process of lime stabilization of wastewater treatment plant sludge. This patent discloses the dewatering of the sludge and intimately mixing calcium oxide to raise the temperature so as to produce a stabilized sludge particle.
None of these prior art inventions are capable of achieving temperatures, when mixed the sludge, of greater than 100.degree. C. None of these prior art techniques allow for the shorter drying times as required by 40 C.F.R. Subchapter O, Part 503.32 a.311.A-D. The shorter drying times, as required by this Subchapter, are in accordance with the following formula: EQU D=131,700,000/(1.times.10**0.14t) (1)
where
D=time in days PA1 t=temperature in degrees Celsius
It is an object of the present invention to provide a process for rendering a biological waste sludge pathogen-free and vector-free.
It is another object of the present invention to provide a process that converts the biological waste sludge into a sellable end product.
It is still a further object of the present invention to provide a process that eliminates or reduces waste incineration and landfilling of waste sludges.
It is another object of the present invention to provide a process that eliminates the odors resulting from lime stabilization.
It is still a further object of the present invention to provide a process that facilitates the dewatering of the biological sludge.
It is still another object of the present invention to provide a process that recycles waste heat.
It is still a further object of the present invention to provide a process for treating waste sludges that is cost effective, easy to use, and easy to install.
These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims.